The present invention relates to a rubber composition for tires, which considers environments and has high-performance, and a pneumatic tire using the same.
Conventionally, a phenol resin or a petroleum resin derived from a fossil fuel such as an petroleum is used in a rubber composition for a tread and a sidewall as a tackifier.
However, because of the recent trend to emphasize global environmental issues and seek for a new tackifier replacing conventional resins derived from petroleum oil which has been conventionally used, it is preferable to employ a tackifier derived from resources other than petroleum such as a vegetable oil in rubber compositions for tires in place of the petroleum oil.
Although rubber compositions using materials derived from resources other than petroleum (biomass materials) such as rosin or terpene resin as a tackifier are known, the tackifier has needs to be improved in its tackiness and other various physical properties. For example, if tackiness is intended to be enhanced with a terpene resin, a method to copolymerize petroleum monomers are employed, which is unfavorable from a view point of considering environments.
JP-A-2005-248056 discloses a rubber composition excellent in grip property and abrasion resistance by compounding a specific amount of a rosin ester resin having specific properties, however, improvement effects of sufficient tackiness is hardly obtained and also in terms of grip property and abrasion resistance, there is a room to be further improved.